Light leakage, how can you tell in real life?

[Serg]

Is 'crashed' ice from an ice truck accident?

Thank You.

Serg, I hope you're not offended if it was you who wrote crashed ice instead of crushed ice.
I have nothing but great respect for you and your work and frankly for anyone who attempts to learn this crazy language we call English.

Kenny, there is not any problem here. We used this chart 1-2 times one year ago.
I do not like this chart because:
1) It has a few cuts. we need add 100+ other cuts( but we have not time to do it well)
2) it use information about just average Flash size, average duration( it does not show variation of these characteristics) . so correct interpretation of chart is difficult ( it is necessary to show many movies , give 2 hours explanations before this chart become clear).
Main idea of this chart is clustering all cuts by few parameters( as flashes size and duration) to help sales person better understand consumer taste.
Firstly sales person shows to consumer 6-9 movies( in same time ) which represent different Types combinations of FlashesSize/FlashesDuration and ask him what he likes.
then sales person show diamonds only from 2-3 groups.( If consumer selected princess at the beginning , it is not good idea to show him a Emerald cut)

 

[Serg]

Is 'crashed' ice from an ice truck accident?

Yes, it makes you wonder if maybe Garry and Serg should proofread their posts and have their work checked and peer reviewed before it is posted here.

Seriously? Peer review before PS publication?
Do you know any person for such work? I happy to do it( free of charge of course)
any real suggestion ?

 

[starrylight]

http://www.octonus.com/oct/mss/diamVC2.html

Out of curiosity, why are emeralds not included? Is there too much cut variation?

 

[Serg]

http://www.octonus.com/oct/mss/diamVC2.html

Out of curiosity, why are emeralds not included? Is there too much cut variation?

we have Goal to design Fancy cuts with similar or better Optical performance than RBC.
I do not see a way how Emerald cut may help us.

 

[kenny]

http://www.octonus.com/oct/mss/diamVC2.html

Out of curiosity, why are emeralds not included? Is there too much cut variation?

we have Goal to design Fancy cuts with similar or better Optical performance than RBC.
I do not see a way how Emerald cut may help us.

It is not an emerald cut, it's a step but but have you seen KarlK's Octavia in person?

 

[Serg]

http://www.octonus.com/oct/mss/diamVC2.html

Out of curiosity, why are emeralds not included? Is there too much cut variation?

we have Goal to design Fancy cuts with similar or better Optical performance than RBC.
I do not see a way how Emerald cut may help us.

It is not an emerald cut, it's a step but but have you seen KarlK's Octavia in person?

No. I happy to see it, but I doubt that I need to see it.

 

[Sunstorm]

Definitely worth seeing IMHO and I really do not generally like step cuts, emerald are my least fave because light performance is crucial to me but Octavias are an entirely different story, I think they are amazing stones and I think it is also good to stay in the loop.

 

[Serg]

Definitely worth seeing IMHO and I really do not generally like step cuts, emerald are my least fave because light performance is crucial to me but Octavias are an entirely different story, I think they are amazing stones and I think it is also good to stay in the loop.

Rectangular Emerald ( Asscher ) has much less problems than Emerald with big ratio, but still has.
some problems in Asscher design are not possible fix just tuning slope angles and increasing corner sides.

there are some fundamental problems in any Step Cuts if opposite facets are big and have azimuth +180 degree.

you may develop Asscher which is much better than any other Asscher but I do not see any way to avoid typical Asscher problems.

 

[kenny]

http://www.octonus.com/oct/mss/diamVC2.html

Out of curiosity, why are emeralds not included? Is there too much cut variation?

we have Goal to design Fancy cuts with similar or better Optical performance than RBC.
I do not see a way how Emerald cut may help us.

It is not an emerald cut, it's a step but but have you seen KarlK's Octavia in person?

No. I happy to see it, but I doubt that I need to see it.

I'm sure diamond cut experts at your level 'get it' with just the data.
Unlike us mortals you don't need to see the stone in person.

I'm just saying that the Octavia has light performance that blows away any other step cut I've seen, with its precision angles and high crown.
Off-axis it still performs .... probably better than any ideal cut rounds I've owned or seen.

So, if step cuts were left off that list because there is no hope for them to compete light performance-wise with other shapes, please reconsider.

 

[Texas Leaguer]

Is 'crashed' ice from an ice truck accident?

Yes, it makes you wonder if maybe Garry and Serg should proofread their posts and have their work checked and peer reviewed before it is posted here.

Alot of what you get here is unvarnished, free-flow discussion. And sometimes you get it from some of the top researchers in the field. It's a mistake to discount any of the ideas exchanged here because they have not had final polish. My advice is to keep an open mind and go with the flow.

 

[Karl_K]

Since my baby was mentioned I have to be real careful not to be self promoting.
So....

If the goal is making all diamonds RB like then studying step-cuts is not going to get you there.
Serg is right there.
In simple terms long vertical facets are different than long horizontal facets in how they interact with the environment and in some ways each other particularly in the pavilion of the diamond.
However that does not mean step cuts can't be just as beautiful and bright and fiery as any other cut and in some cases more so in one way or another they will just never be RB like.

 

[Garry H (Cut Nut)]

I don't agree that large slow flashes are bad, an EC has a lot of them off the main steps and they are pleasing to see.
I do not like forcing all cuts to meet one criteria.

Who did that?

What is not optimal in one design may be optimal in another.

By labeling slow flashes as bad in the chart it implies that they are always bad.


Label are : "Bad Fire Dynamic ", " Good Fire Dynamic"

Where did you find here any thing about "Bad or good diamonds?", "One rule for all diamonds?", Etc,...
It just Fire Dynamic.
A family car has worse dynamic than sport car. Does this statement say that Family car is worse than Sport car?

I also think that labeling fast as good is not right.
I think by reading what you have said over the years we do not really disagree, its the presentation on the chart I disagree with.

Seems, you have not any idea about context this chart.

Garry, please either explain reason of publication the chart by you .( explain full context) . It is not good idea to take on chart from 2 hours presentation without any explanations of chart proposal .

Firstly I have not experience the presentation that this slide came from. Secondly I thought that since the leakage topic has changed to include Fire, that this would be good to help people who are interested to understand more about the complexities of fire. I found it very useful, so I thought others would too. I also noticed the spelling mistake when I first saw it, but I did not think it was worthy of an interruption – most of the people I believed would be seeing it would have English as a second language and anyway, outside of this forum, crushed ice probably has little meaning, so ‘crashed’ would probably prompt people in the audience to ask what it means.

Below is a paragraph from an article soon to be published in an Asian peer reviewed journal. (The first article published in the Australian Gemmologist was peer reviewed. Another article soon to be published in a leading industry commercial journal has been editorially reviewed. We, as a group, have published several articles and while some may find it sloppy that there are researchers whose English is not that great, its not fair to hold us to that same standard in a make it up as you go forum).

Fire appears as separate coloured flashes characterized by brightness, saturation, size, shape, lifetime (duration) and colour gradient. Fire can also have ‘bloom’ and ‘star’ effects (see coloured flash in Fig. 5). Flashes can be slower like brilliance flashes and need not be very bright or can be like scintillation flashes; faster and more intense. A flash must be large enough to be able to be seen at a normal viewing distance, bright enough to stand out from the diamond and its surroundings, and have good colour saturation. Brightness and saturation can be combined into a colour metric called Chroma in the Luv colour science system (Hunt, 2004 [2]). A colour flash also has attributes of shape, and texture or colour gradient that can be seen within a large facet. The size and shape of flashes is a difficult thing to quantify because it is hard to prove which is best when combined with all the variables. For example, is one slow coloured flash as shown in the top of Fig. 7 preferable to the two coloured flashes on either side of the white flash in the lower series? How much better is a red to yellow flash than a blue to violet one as in the two flashes shown in the bottom series of Fig. 7? The Cut Group plans to use a crowd-sourced solution to research, test and provide answers to these questions.

 

[Karl_K]

Since my baby was mentioned I have to be real careful not to be self promoting.
So....

If the goal is making all diamonds RB like then studying step-cuts is not going to get you there.
Serg is right there.
In simple terms long vertical facets are different than long horizontal facets in how they interact with the environment and in some ways each other particularly in the pavilion of the diamond.
However that does not mean step cuts can't be just as beautiful and bright and fiery as any other cut and in some cases more so in one way or another they will just never be RB like.

Which is a good thing because diamonds would be boring if all diamonds were RB like.

 

[Rockdiamond]

Garry- are you speaking of this question, page 2?

Dave,
1) what is Fire for you?
your Comments about Fire looks very strange for me. Please Clarify you Fire definition

I have read the part of the paper where the phenomena is described-
I take it to mean the prism's that come off the diamond when the angular subtend between the pupil, light source and facet plane are properly aligned- is that correct?

Secondly, how did you ever get the idea that the 'fair' stone would be spready - that would not have been the case at all.

I have seen stones that were spready have similar ASET signatures. I didn't say "would" I said "could"

Thirdly, even if such a stone was 10% smaller for the same weight, a diamond like the Ex one will appear larger in most lighting.
Any idea why?

Part of what I have been doing for this discussion is spending time speaking to a few diamond cutters to further refine my understanding.
I have an idea the scientific observations you will point to to back up your statement- however I feel that there's too many variables on the non LP stones we would use to compare.
And why do you assume only 10%?
The difference could be far greater.

Hi Garry- did you see this post of mine?
Was that the answer about fire you were looking for?

Dave,
you just reprinted the reason of Fire from article. You did not answer on question "what is Fire for you?"
what do you see? How do you grade Fire in diamonds? how are You show Fire to your customers? How is important Fire for you and your customers
there is big difference between reason of Phenomena and appearance of Phenomena.

You did not clarify your opinion, your observation. You just gave link to article( which do not describe Fire from Consumer point of view)

Good questions Serg.
Fire, as we're defining it here is one single aspect among many. I don't focus on that single aspect in buying, nor do many consumers ask specifically for it.
Far more important to most people we speak to, and sell to is the entire package.
For example, if the stone is not set properly, it does not matter how well it's cut.
Many well cut fancy shapes are not designed with fire in mind. But again we're looking at a lot of aspects including spread sparkle overall shape.
Bottom line is making sure the buyer is happy.
No matter how well we can document various aspects of cut, it still comes down to the buyer opening the box and being happy.

I sincerely believe that current ASET readings and leakage warnings frequently given here will cause a lot of returns when the buyers actually open the box.